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The present invention relates to connectors and more specifically to a connector that utilizes conductive elastomeric columnar contacts and is adapted for use in board-to-board applications and for coupling integrated circuit sockets to a printed circuit board.
Board-to-board interconnect devices using elastomeric conductive members are known. One such interconnect device is disclosed in U.S. Pat. No. 6,056,557. In this interconnect device, conductive resilient members are disposed in holes in a substrate on a predetermined grid array and the assembly is positioned between adjacent printed circuit boards so as to make conductive contact between conductive pads on opposing boards.
Another device that uses conductive elastomeric columns for interconnecting a semiconductor device to a printed circuit board in disclosed in U.S. Pat. No. 5,624,268.
In board-to-board interconnect applications, however, it is sometimes desirable to have the boards separated by a distance sufficient to permit electrical components and semiconductor devices to be mounted to and between and the opposing printed circuit boards. This application requires that the length of the conductive members be substantially greater than contemplated in prior art connectors employing resilient conductive members. The pre-existing interconnect devices that employ elastomeric conductive column are not of a sufficient height to permit the use of such devices in anything other than a close opposed relationship due to the height of the conductive columns. Moreover, due to the resilience and the instability of the conductive columns as the height of such columns increases, interconnects employing conductive elastomeric columns have not been employed except in applications involving close board-to-board spacings or in applications involving the interconnection of a semiconductor device to a printed circuit board.
Additionally, in certain applications it is desirable to be able to conductively couple an integrated circuit device socket, such as a Bail Grid Array (BGA) device socket or a Land Grid Array (LGA device socket to a printed circuit board. In such applications, the contacts are closely spaced and the connector must maintain tight mechanical tolerances to properly couple the contacts of the respective device socket to the corresponding contacts on the printed circuit board.
Accordingly, it would be desirable to have a connector design that employs conductive elastomeric columnar contacts and that permits board to board interconnections with large interboard spacings. Additionally, it would be desirable if the connector design was suitable for conductively coupling BGA and LGA device sockets to a printed circuit board. It would further be desirable to have a method for producing such connectors in an efficient manner that is applicable to high volume manufacturing techniques.
A connector for use in board-to-board or board to device socket interconnect applications comprises a plurality of conductive elastomeric columnar contacts arranged in a predetermined pattern. The elastomeric columnar contacts are surrounded by a supporting polymer, such as silicone, to provide support for and prevent deformation of the conductive elastomeric columnar contacts.
In one embodiment of the invention, a plurality of conductive elastomeric columnar contacts are supported by a substrate such as a polyimide sheet to form a contact assembly. The contact assembly is positioned within in a mold and an insulative supporting material, such as silicon, is injected into the mold so as to surround the conductive elastomeric columnar contacts. The tips of the conductive elastomeric columnar contacts extend outboard of the surface of the cured insulative supporting material to allow the tips of the columnar contacts to make conductive contact with corresponding pads located on opposing printed circuit boards. To avoid overstress of the tips of the columnar contacts, a stop flange may be provided that limits the deformation of the tip of the elastomeric columnar contact. The stop flange may be provided an a singular raised portion that extends above the opposing surfaces of the body along the periphery of the body surface. Alternatively the stop flange may be provided as a plurality of raised areas that serve to resist compression of the columnar contacts beyond to predefined limit.
In one embodiment, the mold is configured so that the supporting material forms a non-conductive raised collar around the opposing ends of the conductive columns although the tips of the columnar contacts extend beyond the upper surface of the raised collars to allow the tips to make conductive contact with corresponding contacts on a circuit board.
A connector in accordance with the present invention may be produced by molding the body of supporting non-conductive material around the contact assembly. Alternatively, a body of non-conductive supporting material may be molded in a first molding operation and the conductive elastomeric material may be molded into through-holes in the body in a secondary molding operation to form the conductive elastomeric columnar contacts.
Other features, aspects and advantages of the above described connector and methods of making the same will be apparent to those of ordinary skill in the art from the detailed description of the invention that follows.